Cylindrical alkaline cells with increased discharge performance

ABSTRACT

An alkaline battery cell with increased discharge capacity is provided. Both the internal volume and the electrode interfacial surface area are increased, without unnecessarily increasing the overall cell volume, by increasing the height but not the diameter of the electrodes, thereby avoiding an unnecessary increase in the total cell volume.

BACKGROUND

The present invention generally relates to cylindrical alkalinezinc/manganese dioxide electrochemical cell batteries.

Cylindrical alkaline zinc/manganese dioxide batteries are popularsources of power for portable devices used by consumers. They arereadily available, highly reliable and provide good shelf life anddischarge characteristics at a reasonable cost.

Portable devices are increasingly requiring higher rate output (currentand power) capability, as well as increasingly longer discharge timesfrom the batteries that power the devices. At the same time, the trendis toward more compact devices, hence smaller batteries.

One way to achieve higher rate output as well increase discharge timesis to improve battery discharge efficiency. Batteries are able todeliver only a fraction of their theoretical capacity, and, in general,that fraction (the discharge efficiency) decreases as the discharge rateincreases. One factor that can affect the discharge efficiency of abattery is the interfacial surface area between the electrodes in thebattery's cell(s). Increasing the interfacial surface area generally haspositive effects on current density, internal resistance, concentrationpolarization, and other characteristics that can effect dischargeefficiency. Accordingly, the current, power and discharge capacity ofalkaline batteries can be increased by increasing the interfacialsurface area between the anodes and cathodes.

Typical consumer cylindrical alkaline Zn/MnO₂ battery cells have abobbin-type construction, with coaxially disposed electrodes. Thepositive electrode (cathode) has essentially a hollow cylindrical shapewith a smooth, round internal surface disposed next to the cellcontainer's sides. A negative electrode (anode) is disposed within thehollow cavity in the cathode, with a separator between the opposinganode and cathode surfaces (i.e., in the electrode interface). The areaof that interface is the interfacial surface area, which can beapproximated by measuring the area of the inner surface of the hollowcathode cylinder.

There have been previous attempts to improve the high power capabilityand/or the high rate discharge capacity of alkaline batteries byincreasing electrode interfacial area. Examples can be found in U.S.Pat. No. 3,335,031, U.S. Pat. No. 5,869,205, U.S. Pat. No. 6,074,781 andU.S. Pat. No. 6,342,317. However, each of these references suffers fromone or more of the following disadvantages, particularly for smalldiameter, small volume cells such as AAA/LR03 and AAAA/LR8D425 sizes.

Manufacture of cells is difficult when a current collector prong mustextend into each of a plurality of like-polarity electrodes. This meansthat each current collector prong must be aligned with one of theplurality of electrodes, requiring orientation of both the cell and thecurrent collector. In addition, when multiple current collector prongsare required, the volume of active materials must be reduced to allowfor an increase in the total volume of the collector, compared to celldesigns in which a single current collector prong will suffice.

When the shape of the electrode interface is not essentially a rightcylinder (e.g., when there are radial projections), the separator can bedifficult to insert because of irregular surfaces and small clearances.Typical separator materials (e.g., polymeric film and woven or non-wovenpaper or fabric) in strip or sheet form may not conform well to thesurface of the cavity in the cathode. Even application of a spray-onseparator to the interfacial surface of one of the electrodes can bedifficult. Sharp corners and narrow recesses in the interfacial surfaceof the cathode can make it difficult to completely fill the cavitieswith anode material, especially at high manufacturing speeds. Activematerials can be non-uniformly, therefore incompletely, consumed duringdischarge because the maximum distance from the electrode interface (andthe opposite electrode) can vary considerably in different parts of bothelectrodes. Electrode lobes can be more fragile, resulting in damageduring assembly and short circuits within the cells.

The relative increase in separator volume can be greater than theincrease in anode and cathode volumes, at least partially offsettingincreases in discharge capacity that could be achieved through improveddischarge efficiency with decreases due to relative reductions in theamounts of active materials.

Another way to increase the discharge capacity of a battery is toincrease the amount of active materials that are put into the cell. Thiscan be difficult if the external dimensions of the battery are notincreased, as may be the case when maximum dimensions are specified, asis often the case for standard battery types in various industrystandards. Examples of this approach are found in U.S. Pat. Nos.5,283,139 and 6,265,101. Each of these references suffers from thedisadvantage that the maximum dimensions are maintained, limiting theamount of possible increase in the amount of active materials (andtherefore the theoretical capacity) in the batteries.

Since it is often desirable to minimize the size of portable devices, itis likewise desirable to minimize the volume of the batteries that powerthose devices.

For the foregoing reasons there is a need for a cylindrical alkalinecell with increased theoretical capacity as well as increased dischargeefficiency, while minimizing the increase in cell volume.

SUMMARY

We have developed an extended interfacial surface area cylindricalalkaline cell that minimizes the impact on overall cell volume byextending the length of the anode and cathode while maintaining the sameanode and cathode diameters.

A first aspect of the invention is an alkaline battery cell thatcomprises a cylindrical cell container having a straight side wall, aclosed bottom end, and an open top end; a positive electrode containingelectrolytic manganese dioxide; a negative electrode containing zinc; aseparator; an electrolyte comprising a potassium hydroxide solute inwater; and a closing element closing the open end of the container andsealing the electrodes and electrolyte within the cell. The positiveelectrode has a hollow cylindrical shape and is disposed against theside wall and the bottom end of the container to form a cavity. Thenegative electrode is disposed within that cavity, and the separator isdisposed between the negative electrode and both the positive electrodeand the bottom of the container. The container straight side wall has anoutside diameter of 7.3 to 14.5 mm, and the positive electrode has aheight of 45.7 to 76.2 mm from the bottom of the container.

In embodiments of the invention, the container straight side walldiameter and positive electrode height are 9.0 to 10.5 mm and 53.4 to68.6 mm, 7.3 to 8.3 and 45.7 to 61.2, and 13.1 to 14.5 mm and 58.4 to76.2 mm, respectively.

A second aspect of the invention is an alkaline battery cell thatcomprises a cylindrical cell container having a straight side wall, aclosed bottom end, and an open top end; a positive electrode containingelectrolytic manganese dioxide; a negative electrode containing zinc; aseparator; an electrolyte comprising a potassium hydroxide solute inwater; and a closing element closing the open end of the container andsealing the electrodes and electrolyte within the cell. The positiveelectrode has a hollow cylindrical shape and is disposed against theside wall and the bottom end of the container to form a cavity. Thenegative electrode is disposed within that cavity, and the separator isdisposed between the negative electrode and both the positive electrodeand the bottom of the container. The container straight side wall has anoutside diameter of outside diameter of 9.0 to 10.5 mm and the positiveelectrode has a height of 55.9 to 68.6 mm from the bottom of thecontainer. The cell theoretical capacity is greater than 2500 mAh, thepositive electrode has a surface for interfacing the negative electrodevia the separator, and the interfacial surface has area greater than12.0 cm², the positive electrode has a volume greater than 1.9 cm³, andthe positive electrode further comprises graphite, and a weight ratio ofelectrolytic manganese dioxide to graphite is greater than 19:1.

These and other features, advantages and objects of the presentinvention will be further understood and appreciated by reference to thefollowing specification, claims and accompanying drawings.

Unless otherwise specified, the following definitions and methods areused herein:

(1) “Solid materials” means materials that do not have significantsolubility (i.e., less than 1 percent based on the weight of water) inaqueous KOH solution anywhere in the range from 20 to 50 percent KOH byweight.

(2) Solid materials content (i.e., percent solids and percent solidspacking) can be determined by dividing the sum of the volumes of all ofthe solid materials in that electrode by the total volume of thatelectrode and multiplying the result by 100 percent.(3) The volume of a solid material in an electrode can be determined bydividing the weight of that material by its real density, as determinedby helium pychnometry or a comparable method.(4) “Electrode porosity” means the volume percent of non-solid materialsin the electrode and may be determined by dividing the sum of thevolumes of non-solid materials (liquids, materials dissolved in theliquids, and entrapped gases) by the total volume of the electrode. Whenexpressed as a percent, the porosity of an electrode is equal to 100%minus the volume percent solids of the electrode.(5) “Electrode volume” means volume within the exterior surfaces of theelectrode (anode or cathode).(6) “Electrode interfacial surface” means the surface of an electrodethat is adjacent to an electrode of opposite polarity. While the shapesand sizes of interfacial surfaces of adjacent electrodes are usuallyvery similar to one another in order to most efficiently use theinternal volume of the cell, one electrode may extend slightly beyondthe other to prevent internal shorting and accommodate variability inmanufacturing. The interfacial surface area is the area of the entireinterfacial surface, including any portion thereof that may extendbeyond the corresponding interfacial surface of the adjacent electrode.(7) The theoretical capacity of an electrode is a calculated capacity inampere hours (Ah) based on the specific capacity (capacities) (in Ah pergram) of the active material (materials) in the electrode, assuming thatall of the active material (materials) reacts according to the nominaldischarge reactions. Unless otherwise indicated or apparent, thespecific capacity used herein for electrolytic manganese dioxide thespecific capacity is 0.379 Ah/g, assuming that all of the manganesereacts to Mn^(+2.67) (an average of about 1.33 electrons per Mn atom),and the specific capacity of zinc is 0.820 Ah/g. The theoreticalcapacity of a cell is equal to that of the lower capacity electrode (thelimiting electrode). Alternatively, capacity can be expressed inmilliamp hours (mAh).(8) “Long AAA cell” is a cell that has a diameter that would be suitablefor a cell used in a battery meeting the dimensional requirements of anLR03 battery as specified in American National Standard for Dry Cellsand Batteries—Specifications, ANSI C18.1.(9) “Long AAAA cell” is a cell that has a diameter that would besuitable for a cell used in a battery meeting the dimensionalrequirements of an LR8D425 battery as specified in American NationalStandard for Dry Cells and Batteries—Specifications, ANSI C18.1.

Unless otherwise specified herein, all disclosed characteristics andranges are as determined at room temperature (20-25° C.).

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows average discharge curves (voltage vs. time on discharge)for long AAA cells on four constant power discharge tests;

FIG. 2 shows average discharge curves for long AAA cells, LR03 cells andLR6 cells on a 1000 mW continuous discharge test; and

FIG. 3 shows average discharge curves for long AAAA cells on threeconstant power discharge tests.

DESCRIPTION

The alkaline battery cell of the invention is a cell with increaseddischarge capacity. In the cell of the invention, both the internalvolume and the electrode interfacial surface area are increased, withoutunnecessarily increasing the overall cell volume. For cells with acylindrical anode surrounded by a cylindrical cathode (typical ofstandard cylindrical alkaline cells), such an increase can be achievedeither by increasing the diameter of the cylindrical anode (and therebyalso increasing the inner diameter of the surrounding cathode),increasing the length of the anode and cathode, or increasing both thediameter and length of the anode and cathode. All other factorsremaining equal, interfacial surface area will increase in proportion tothe increase in the aforementioned diameters and/or in proportion to theamount of the increase in the aforementioned lengths. For example, a 10%increase in the anode diameter of a cell with concentric cylindricalelectrodes will result in a 10% increase in the electrode interfacialsurface area. A 10% increase in the length of the anode and surroundingcathode will also result in a 10% increase in the interfacial surfacearea. Both of these solutions will increase the cell volume. However, a10% increase in the length of the anode and surrounding cathode willresult in an increase of at least 10% in total cell volume, while a 10%increase in the diameter of the anode will result in an increase of atleast 21%. Thus, it is desirable to increase interfacial electrodesurface area by only increasing the length of the anode and surroundingcathode, not the diameter, as the impact on overall cell volume is lessthan if the diameter were also increased.

The cell of the invention may have the same basic design and activematerials as an existing cell, but with a longer cell container toaccommodate the taller electrodes. LR03 and LR8D425 battery cells arecylindrical Zn/MnO₂ cells containing an aqueous alkaline electrolyte,normally having KOH as a solute. LR03 and LR8D425 cells can be modifiedas described above to produce long AAA and long AAAA cells,respectively. Alternatively, other cell features, such as seals, covers,current collectors, electrode compositions, electrolyte composition andthe like, may also be modified.

EXAMPLE 1

Long AAA cylindrical alkaline cells were made with a diametercorresponding to the diameter of conventional LR03 cells and a heightcorresponding to 1.5 times the height of conventional LR03 cells. Thecells had a bobbin-type construction. Each long AAA cell included acylindrical steel can with closed bottom and open top ends, a cathode inthe form of a hollow right cylinder formed against the inside surface ofthe can side wall, an anode disposed within the cavity formed by theinner surface of the cathode and the bottom of the can, a separatordisposed between the anode and both the cathode and can bottom, and aseal and collector assembly closing the open end of the can.

The cell design principles set forth in United Kingdom patentapplication numbers GB 0015003.7, GB 0113990.6, GB 0113991.4 and GB0120824.8 were followed. For example, the anode porosity was at least69%, the cathode porosity was at least 26% and the electrolyteconcentration was selected so that the final KOH concentration after a1-electron discharge was between 49.5% and 51.5% (weight/weight cell).

Each cell contained 7.32 grams of cathode mixture, 4.31 grams of anodemixture and 1.04 grams of electrolyte solution and had a 5.0 volumepercent void volume within the sealed cell.

Each cathode was made by forming cathode mixture into ring-shapedpellets, pushing 6 pellets into each can, with an interference fitbetween the pellets and can. A piece of coated separator paper wasscrolled into a tube, folded into a basket shape and placed into thecavity formed by the cathode and can bottom. Anode gel mixture and freeelectrolyte were added to the cell. The cell was closed with a seal andcollector assembly, with a pin-shaped current collector extending intothe centrally disposed anode.

The cell cans were made in a conventional manner from conventionalmaterial cold-rolled steel strip, plated on the exterior surface withnickel. The cathode-contacting interior surfaces of the cans were coatedwith EB099, a graphite coating material available from Acheson ColloidsCompany, Port Huron, Mich., USA. The overall can height was 64millimeters and the overall diameter was 10 millimeters.

The cathode mixture used in the Example 1 cells had a 23:1 ratio of EMDgraphite and included Kerr McGee EMD (94.30 weight percent), SuperiorGraphite expanded graphite (4.10 weight percent) and 40 weight percentKOH in water (1.60 weight percent). Each cathode pellet weighed 1.22grams had an outside diameter of 9.60 mm and a height of 9.80 mm beforeinsertion and an inside diameter of 6.30 after insertion into the cans,resulting in a final cathode porosity of 30.0 volume percent.

The anode mixture had a 69.50 volume percent porosity and included 64.10weight percent zinc powder (BIA 110, containing a Bi—In—Al zinc alloyand having a d₅₀ of 110 μm, from Umicore, Brussels, Belgium), 5.60 zincflake (grade 5454.3, containing a Bi—In—Al zinc alloy, from TransmetCorp., Columbus, Ohio, USA), 0.38 weight percent gelling agent(CARBOPOL® 940 acrylic acid in 100% acid form from B. F. GoodrichSpecialty Chemicals, Cleveland, Ohio, USA), 0.02 weight percent indiumhydroxide, 0.04 weight percent zinc oxide, and 29.86 weight percent KOHsolution consisting of 38 weight percent KOH in water.

The separator had 2 layers of VLZ75 separator paper (from Nippon KodoshiCorp., Kochi-ken, Japan), coated to 30 grams/m² of poly (acrylicacid-co-sodium-4-styrene sulfonate), in a 20:80 ratio of acrylicacid:sodium styrene sulfonate, as disclosed in United Kingdom patentapplication number GB 0113989.8.

EXAMPLE 2

Long AAAA cylindrical alkaline cells were made with a diametercorresponding to the diameter of conventional LR8D425 cells and a heightcorresponding to 1.5 times the height of conventional LR8D425 cells.These cells were made in the same manner as disclosed for the cells inExample 1, except for the following.

Each cell contained 3.71 grams of cathode mixture, 1.80 grams of anodemixture and 0.90 gram of electrolyte solution and had a 3.5 volumepercent void volume within the sealed cell.

The cell cans had an overall can height of 59.25 millimeters and anoverall diameter of 7.6 millimeters.

Each cathode pellet weighed 0.62 gram had an outside diameter of 7.11 mmand a height of 8.50 mm before insertion and an inside diameter of 4.55after insertion into the cans, resulting in a final cathode porosity of29.0 volume percent.

The anode mixture had a 68.00 volume percent porosity and included 71.00weight percent zinc powder, no zinc flake, 0.36 weight percent gellingagent, 0.02 weight percent indium hydroxide, 0.04 weight percent zincoxide, and 28.58 weight percent KOH solution consisting of 38 weightpercent KOH in water.

EXAMPLE 3

Samples were selected from available cylindrical alkaline LR8D425, LR03and LR6 batteries for comparative discharge testing.

EXAMPLE 4

Cells from Examples 1, 2 and 3 were discharged under various constantpower discharge regimens, as indicated in Tables 1 and 2, to 1.1 volts.The results are compared in Tables 1 and 2. In Table 1, dischargeduration is shown in hours or minutes. In Table 2, discharge durationresults are normalized to the LR03 cells on each test (i.e., 100% is thedischarge duration of LR03 cells on a given test, and 150%, e.g., wouldbe 150% times the discharge duration of LR03 cells on the same test).

TABLE 1 Capacity 100 mW 250 mW 400 mW 1000 mW Cell Type (Ah) (hours)(hours) (hours) (minutes) LR8D425 0.7 4.0 0.6 0.3 Example 2 1.0 6.0 1.40.5 LR03 1.4 10.0 1.9 0.8 4 Example 1 2.1 17.0 4.8 1.9 16 LR6 3.0 26.06.9 2.7 22

TABLE 2 Capacity 100 mW 250 mW 400 mW 1000 mW Cell Type (Ah) (%) (%) (%)(%) LR8D425 0.7 40 32 38 Example 2 1.0 60 74 62 LR03 1.4 100 100 100 100Example 1 2.1 170 253 238 400 LR6 3.0 260 367 338 550

Typical discharge curves for long AAA cells from Example 1 on theconstant power tests done in Example 4 are shown in FIG. 1, in whichvoltage on discharge is plotted over the time on discharge.

FIG. 2 compares a typical discharge curve for Example 1 long AAA cellson the 1000 mW continuous discharge test with typical discharge curvesfor LR03 and LR6 cells from Example 3.

Typical discharge curves for Example 2 long AAAA cells on the 100, 250and 400 mW constant power tests are shown in FIG. 3.

From the results in Table 1, capacity (mWh) was calculated and plottedas a function of cell external volume. On each of the four tests, thelong AAA cells 1 had higher average capacities than would be expectedbased on a straight-line interpolation between the data points for theLR03 and LR6 cells on the same tests. The average capacities of the longAAA cells were about 107%, 114%, 138% and 134% better than theinterpolated capacities on the 100, 250, 400 and 1000 mW tests,respectively.

For long AAAA cells from Example 2, no capacity advantage relative tostraight-line interpolations between LR8D425 and LR03 cells on a plot ofcapacity vs. total cell volume were observed. This may have been due todeficiencies in the long AAAA cells due to difficulties in assemblingthe long AAAA cells.

EXAMPLE 5

Long AAA cylindrical alkaline cells were made in accordance with theinvention in the same manner as disclosed for the long AAA cells inExample 1, except as shown in Table 3. The quantities of all cellingredients are based on the input amounts, and assuming there are nolosses (e.g., water evaporation) during manufacturing. The cell designprinciples set forth in United Kingdom patent application numbers GB0015003.7, GB 0113990.6, GB 0113991.4 and GB 0120824.8 were notnecessarily followed in the long AAA cells in Example 5. The increasesin active materials compared to the cells in Example 1 were possible inpart by the use of a lower volume seal and collector assembly. The longAAA cell of Example 5 had a theoretical discharge capacity greater than2500 mAh, a cathode interfacial surface area greater than 12.0 cm², acathode volume greater than 1.9 cm³, and a MnO₂:carbon weight ratiogreater than 19:1.

TABLE 3 Example 5 Example 6 Example 6 Cell Parameter Long AAA LR03 LR6Cell content cathode mixture (g) 8.00 5.00 11.12 anode mixture (g) 4.802.92 6.45 electrolyte soln. (g of 40 wt % aq. KOH) 0.88 0.63 0.125overall cell KOH concentration (wt %) 32.57 31.97 33.93 theor. capacity(mAh) based on anode 2755 1676 3914 Can characteristics outside diameterof can body (in./mm) 0.393/9.98  0.393/9.98  0.547/13.89 inside diameterbelow step (in./mm) 0.377/9.58  0.377/9.58  0.527/13.39 wall thicknessbelow step (in./mm) 0.008/0.20  0.008/0.20  0.010/0.25  bottom thickness(in./mm) 0.010/0.25  0.010/0.25  0.010/0.25  graphite can coatingmaterial Acheson LB1099 Acheson LB1099 Acheson LB1099 Separator materialFreudenburg Freudenburg Freudenburg FS28224 FS28224 FS28224 no. oflayers 2.44 2.17 2.14 Cathode ring weight (g) 1.33 1.25 2.78 OD beforeinsertion (in./mm) 0.377/9.58  0.377/9.58  0.527/13.39 ID beforeinsertion (in./mm) 0.2575/6.54  0.258/6.55  0.350/8.89  height beforeinsertion (in./mm) 0.405/10.29 0.377/9.58  0.421/10.69 no. per cell 6 44 Formed cathode ID (in./mm) 0.2575/6.54  0.258/6.55  0.350/8.89  height(in./mm) 2.405/61.09 1.501/38.13 1.667/42.34 interfacial surf. area(in.²/cm²) 1.945/12.55 1.215/7.84  1.831/11.81 volume (in.³/cm³)0.125/2.053 0.078/1.284 0.160/2.626 solids packing (vol. %) 78.01 79.3376.60 Cathode mixture EMD (wt %) 90.96 91.17 90.96 expanded graphite (wt%) 4.49 4.86 4.49 Nb-doped TiO₂ (wt %) 0.39 0.40 0.40 polyethylenebinder (wt %) 0.44 0.45 0.44 KOH solution amount (wt %) 3.72 3.13 3.72KOH conc. in solution (wt %) 40 40 40 MnO₂: C (by weight) 20.3 18.8 20.3Anode mixture Zn powder (wt %) 67.00 67.00 68.00 Zn flake (wt %) 3.003.00 2.40 Carbopol 940 (wt %) 0.479 0.460 0.445 ZnO (wt %) 0.976 0.9360.906 KOH solution amount (wt %) 32.52 31.20 30.19 KOH conc. in solution(wt %) 32.00 32.00 36.00 sodium silicate (wt %) 0.098 0.094 0.091Electrolyte additions KOH solution amount (g) 0.88 0.63 1.25 KOH conc.in solution (wt %) 36.5 36.5 36.5

EXAMPLE 6

Batteries with parameters closest to those of the Example 5 long AAAcells were selected from LR03 and LR6 cells that were available. Table 3above includes key parameters of these LR03 and LR6 cells.

EXAMPLE 7

Cells from Examples 5 and 6 were tested at 21° C. (70° F.) on severalcontinuous constant current and constant power discharge tests. Averagecapacities to 1.0 volt are summarized in Table 4.

TABLE 4 Discharge Capacity Example 5 Example 6 Example 6 Test Long AAALR03 LR6 1500 mA continuous  394.7 mAh  161.0 mAh  478.3 mAh 1000 mAcontinuous  557.4 mAh  273.6 mAh  707.0 mAh  500 mA continuous  818.2mAh  432.4 mAh 1100.3 mAh  250 mA continuous 1132.7 mAh  671.2 mAh1711.9 mAh  100 mA continuous 1650.3 mAh  998.2 mAh 2265.8 mAh 1000 mWcontinuous  555.1 mWh  269.8 mWh  653.5 mWh  400 mW continuous 1022.8mWh  534.0 mWh 1310.0 mWh  250 mW continuous 1281.3 mWh  702.3 mWh1741.6 mWh  100 mA continuous 1695.1 mWh 1000.2 mWh 2278.4 mWh

EXAMPLE 8

Using the results of the testing in Example 7, long AAA cell dischargecapacity (mWh) on constant power discharge, as a function of both totalcell volume and cathode volume, was compared to discharge capacities ofthe LR03 and LR6 cells according to the Interpolation Method below. Asshown in Table 5, the discharge capacity of the long AAA cell is greaterthan would be expected on each test, based on straight-lineinterpolations between the LR03 and LR6 results.

The results in Table 5 are consistent with those described in Example 4above, with actual capacities exceeding those that would be expectedbased on straight-interpolations between data points for cell types withlarger and smaller volumes than the long AAA cells. This is true whethera plot of capacity vs. total cell volume or capacity vs. cathode volumeis used. There is also a direct correlation between the magnitude ofthis advantage and increasing constant discharge power.

TABLE 5 Actual Inter- Capacity polated Actual (% of Graph Used: CapacityCapacity interpolated Test Capacity vs. — (mWh) (mWh) capacity) 1000 mWcont. Total Volume 475 555 117%  400 mW cont. Total Volume 870 1023 118% 250 mW cont. Total Volume 1150 1281 111%  100 mW cont. Total Volume1540 1695 110% 1000 mW cont. Cathode Volume 460 555 121%  400 mW cont.Cathode Volume 915 1023 112%  250 mW cont. Cathode Volume 1215 1281 105% 100 mW cont. Cathode Volume 1630 1695 104%

INTERPOLATION METHOD

(1) A tall cell and two comparative cells are selected according to thefollowing criteria:

(a) each cell type has a cylindrical container with coaxial positive andnegative electrodes, a separator between the electrodes, an electrolyte,and a closing element; the positive electrode comprises electrolyticmanganese dioxide, has a hollow cylindrical shape, and is formed againstthe container body side wall and bottom to form a cavity within thecylinder; the negative electrode comprises zinc and is disposed withinthe cavity formed by the positive electrode and the container bottom;the electrolyte comprises a potassium hydroxide solute in water; and theclosing element closes the open end of the container and seals theelectrodes and electrolyte within the cell;

(b) in all cell types the cathode mixtures contain the same types ofmaterials; excluding water and KOH, the ratio of weight percentelectrolytic manganese dioxide in the cathode mixture of the tall cellto that in each of the comparative cells is within the range 0.99:1 to1.01:1, and excluding water and KOH, the ratio of weight percent of eachother ingredient in the cathode mixture of the tall cell to that in eachof the comparative cells is within the range 0.90:1 to 1.10:1;

(c) in all cell types the anode mixtures contain the same types ofmaterials; excluding water and KOH, the ratio of weight percent of totalzinc in the tall cell to that in each of the comparative cells is withinthe range 0.99:1 to 1.01:1, and excluding water and KOH, the ratio ofweight percent of each other ingredient in the tall cell to that in eachof the comparative cells is within the range 0.90:1 to 1.10:1;

(d) the ratio of the percent of total water (as a weight percent of thesum of the anode mixture, cathode mixture, KOH solution and water) inthe tall cell to that in each of the other cells is within the range0.98:1 to 1.02:1, and the ratio of overall KOH concentration (as aweight percent of the total KOH and water) in the tall cell to that ofeach of the comparative cells is within the range 0.95:1 to 1.05:1,assuming no water loss during cell manufacturing; and

(e) each cell type has the same type of separator material, and theratio of separator volume (cm³) per cathode interfacial surface area(cm²) for the tall cell to that of each of the comparative cells iswithin the range 0.99:1 to 1.01:1;

(2) discharge at least one cell of each type continuously at 1000 mW to1.0 volt at room temperature and determine an actual discharge capacityin mWh for each type;

(3) plot a data point representing an average for each cell type on agraph with discharge time on the x-axis and one of total cell volume andcathode volume on the y-axis;

(3) draw a straight line between the data points for the comparativecell types;

(4) on the straight line, find the point corresponding to the volume ofthe tall cell type and determine the corresponding interpolated tallcell discharge capacity on the y-axis; and

(5) compare the interpolated discharge capacity from step (4) with thetall cell actual discharge capacity from step (2).

LR03 battery cell containers may have diameters ranging from 0.359 to0.413 inch (9.0 to 10.5 mm) depending in part on the thickness of anyjacket that may be applied around the cylindrical container. Similaradvantages might also be seen in cylindrical alkaline cells having otherdiameters, such as long AAAA cells (container diameters from 0.288 to0.327 inch (7.3 to 8.3 mm)), long AA cells (container diameters from0.516 to 0.571 inch (13.1 to 14.5 mm), and others. Accordingly, longbattery cell container diameters can range from about 0.288 to 0.571inch (14.5 mm).

Long cell cathode heights can range from about 1.4 to 1.8 times thecathode heights of conventional cells of the same diameters, the highercathode heights being preferred when, for example, the cell closingelement volume can be reduced to allow more space for active materials.For LR8D425, LR03 and LR6 diameters, this includes a range of about 1.8to 3.0 inches (45.7 to 76.2 mm) for the corresponding long cells, orabout 1.8 to 2.7 inches (45.7 to 68.6 mm) for long cells with LR8D425and LR03 diameters. A long AAA cell can have a cathode height of about2.1 to 2.7 inches (53.4 to 68.6 mm), and under certain conditionspreferably at least 2.2 or 2.4 inches (55.9 or 61.0 mm). A long AAAAcell can have a cathode height of about 1.8 to 2.4 inches (45.7 to 61.2mm), preferably at least 2.0 inches (50.8 mm). A long AA cell can have acathode height of about 2.3 to 3.0 inches (58.4 to 76.2 mm), preferablyat least 2.5 inches (63.5 mm).

Further improvements in cell discharge performance can also be made bychanging other cell features that do not increase the diameter of thecell container. For example, the volume of inert cell components (e.g.,cell container, closing element, current collectors, and separator) canbe reduced, making more internal volume available for active materials.The formulations of electrodes and electrolyte can be changed to improvetheoretical capacity and/or discharge efficiency. The electrodeingredients (e.g., types and relative quantities of manganese dioxide,graphite or other conductive material, binder, zinc, anode gellant,potassium hydroxide and various electrode additives) can be changed togive better discharge performance. Current collector materials, shapes,sizes and coatings can also be changed, as can the shapes of theelectrodes.

It may also be possible to achieve similar benefits in cells havingdifferent electrochemical systems (active materials and electrolytes)and different shapes (e.g., prismatic cells).

Although the present invention has been described in considerable detailwith reference to certain preferred versions thereof, other versions arepossible, and examples are disclosed above.

1. An alkaline battery cell comprising: a cylindrical cell containercomprising a straight side wall, a closed bottom end, and an open topend; a positive electrode comprising electrolytic manganese dioxide, anegative electrode comprising zinc, a separator, and an electrolytecomprising a potassium hydroxide solute in water disposed inside thecontainer; a closing element closing the open end of the container andsealing the electrodes and electrolyte within the cell; wherein: thepositive electrode has a hollow cylindrical shape and is disposedagainst the side wall and the bottom end of the container to form acavity within the hollow cylinder, the negative electrode is disposedwithin the cavity in the positive electrode, and the separator isdisposed between the negative electrode and both the positive electrodeand the bottom of the container; the container straight side wall has anoutside diameter of 7.3 to 14.5 mm; and the positive electrode has aheight of 45.7 to 76.2 mm from the bottom of the container.
 2. The cellaccording to claim 1, wherein the container outside diameter is 9.0 to10.5 mm and the positive electrode height is 53.4 to 68.6 mm.
 3. Thecell according to claim 2, wherein the positive electrode height is atleast 55.9 mm.
 4. The cell according to claim 3, wherein the positiveelectrode height is at least 61.0 mm.
 5. The cell according to claim 2,wherein the theoretical cell capacity is greater than 2500 mAh.
 6. Thecell according to claim 5, wherein the positive electrode has a surfacefor interfacing the negative electrode via the separator, and theinterfacial surface has area greater than 12.0 cm².
 7. The cellaccording to claim 6, wherein the volume of the positive electrode isgreater than 1.9 cm³.
 8. The cell according to claim 2, wherein thepositive electrode further comprises graphite, and a weight ratio ofelectrolytic manganese dioxide to graphite is greater than 19:1.
 9. Thecell according to claim 2, wherein the total potassium hydroxideconcentration in the cell prior to discharge, based on the total amountsof potassium hydroxide and water, is such that the calculated potassiumhydroxide concentration is between 49.5 and 51.5 percent (w/w solution)if the cell were discharged to reduce the manganese in the manganesedioxide to Mn⁺³.
 10. The cell according to claim 1, wherein thecontainer outside diameter is 7.3 to 8.3 mm and the positive electrodeheight is 45.7 to 68.6 mm.
 11. The cell according to claim 10, whereinthe positive electrode height is at least 50.8 mm.
 12. The cellaccording to claim 1, wherein the container outside diameter is 13.1 to14.5 mm and the positive electrode height is 58.4 to 76.2 mm.
 13. Thecell according to claim 12, wherein the positive electrode height is atleast 63.5 mm.
 14. An alkaline battery cell comprising: a cylindricalcell container comprising a side wall, a closed bottom end, and an opentop end; a positive electrode comprising electrolytic manganese dioxide,a negative electrode comprising zinc, a separator, and an electrolytecomprising a potassium hydroxide solute in water disposed inside thecontainer; a closing element closing the open end of the container andsealing the electrodes and electrolyte within the cell; wherein: thepositive electrode has a hollow cylindrical shape, disposed against theside wall and the bottom end of the container to form a cavity withinthe hollow cylinder, negative electrode is disposed within the cavity inthe positive electrode, and the separator is disposed between thenegative electrode and both the positive electrode and the bottom of thecontainer; the container has an outside diameter of 9.0 to 10.5 mm; thepositive electrode has a height of 55.9 to 68.6 mm from the bottom ofthe container; the cell theoretical capacity is greater than 2500 mAh;the positive electrode has a surface for interfacing the negativeelectrode via the separator, and the interfacial surface has areagreater than 12.0 cm²; the positive electrode has a volume greater than1.9 cm³; and the positive electrode further comprises graphite, and aweight ratio of electrolytic manganese dioxide to graphite is greaterthan 19:1.
 15. An alkaline battery cell comprising: a cylindrical cellcontainer comprising a straight side wall, a closed bottom end, and anopen top end; a positive electrode comprising electrolytic manganesedioxide, a negative electrode comprising zinc, a separator, and anelectrolyte comprising a potassium hydroxide solute in water disposedinside the container; a closing element closing the open end of thecontainer and sealing the electrodes and electrolyte within the cell;wherein: the positive electrode has a hollow cylindrical shape and isdisposed against the side wall and the bottom end of the container toform a cavity within the hollow cylinder, the negative electrode isdisposed within the cavity in the positive electrode, and the separatoris disposed between the negative electrode and both the positiveelectrode and the bottom of the container; the container straight sidewall has an outside diameter of 9.0 to 10.5 mm; the positive electrodehas a height of 53.4 to 68.6 mm from the bottom of the container; andthe cell has an actual discharge capacity in milliwatt-hours that is atleast 110 percent of an interpolated cell discharge capacity, wheninterpolated from discharge testing of an LR03 cell and an LR6 cellaccording to an interpolation method.
 16. The cell according to claim15, wherein the positive electrode has a surface for interfacing thenegative electrode via the separator, and the interfacial surface hasarea greater than 12.0 cm².
 17. The cell according to claim 16, whereinthe volume of the positive electrode is greater than 1.9 cm³.
 18. Thecell according to claim 17, wherein the positive electrode height is atleast 55.9 mm.
 19. The cell according to claim 18, wherein the positiveelectrode height is at least 61.0 mm.